package com.hd.manager.auth;

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.codec.binary.Base64;

import javax.crypto.Cipher;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * <p>
 * RSA加密 工具类
 * </p>
 *
 * @author Administrator
 * @since 2019-04-09
 */
@Slf4j
public class RSAEncryptUtils {
    //用于封装随机产生的公钥与私钥
    private final ConcurrentMap<Integer, String> keyMap = new ConcurrentHashMap<>();

    private static volatile RSAEncryptUtils instance = null;

    private RSAEncryptUtils() {
    }

    public static RSAEncryptUtils getInstance() {
        if (instance == null) {
            synchronized (RSAEncryptUtils.class) {
                if (instance == null) {
                    try {
                        instance = new RSAEncryptUtils();
                        instance.genKeyPair();
                    } catch (NoSuchAlgorithmException e) {
                        log.error("RSA加密工具类实例化失败!", e);
                    }
                }
            }
        }
        return instance;
    }

    /**
     * 随机生成密钥对
     *
     * @throws NoSuchAlgorithmException
     */
    public void genKeyPair() throws NoSuchAlgorithmException {
        // KeyPairGenerator类用于生成公钥和私钥对，基于RSA算法生成对象
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
        // 初始化密钥对生成器，密钥大小为512-1024位
        keyPairGen.initialize(512, new SecureRandom());
        // 生成一个密钥对，保存在keyPair中
        KeyPair keyPair = keyPairGen.generateKeyPair();
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();   // 得到私钥
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();  // 得到公钥
        String publicKeyString = new String(Base64.encodeBase64(publicKey.getEncoded()));
        // 得到私钥字符串
        String privateKeyString = new String(Base64.encodeBase64((privateKey.getEncoded())));
        // 将公钥和私钥保存到Map
        keyMap.put(0, publicKeyString);  //0表示公钥
        keyMap.put(1, privateKeyString);  //1表示私钥
    }

    /**
     * RSA公钥加密
     *
     * @param dou 加密金额
     * @return 密文
     * @throws Exception 加密过程中的异常信息
     */
    public String encrypt(Double dou) throws Exception {
        return this.encrypt(String.valueOf(dou));
    }

    /**
     * RSA公钥加密
     *
     * @param str 加密字符串
     * @return 密文
     * @throws Exception 加密过程中的异常信息
     */
    public String encrypt(String str) throws Exception {
        //公钥
        String publicKey = keyMap.get(0);
        //base64编码的公钥
        byte[] decoded = Base64.decodeBase64(publicKey);
        RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA")
                .generatePublic(new X509EncodedKeySpec(decoded));
        //RSA加密
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, pubKey);
        String outStr = Base64.encodeBase64String(cipher.doFinal(str.getBytes("UTF-8")));
        return outStr;
    }

    /**
     * RSA私钥解密
     *
     * @param str 加密字符串
     * @return 明文
     * @throws Exception 解密过程中的异常信息
     */
    public String decrypt(String str) throws Exception {
        //私钥
        String privateKey = keyMap.get(1);
        //64位解码加密后的字符串
        byte[] inputByte = Base64.decodeBase64(str.getBytes("UTF-8"));
        //base64编码的私钥
        byte[] decoded = Base64.decodeBase64(privateKey);
        RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA")
                .generatePrivate(new PKCS8EncodedKeySpec(decoded));
        //RSA解密
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, priKey);
        String outStr = new String(cipher.doFinal(inputByte));
        return outStr;
    }

    /**
     * 测试用例
     *
     * @param args
     * @throws Exception
     */

    public static void main(String[] args) throws Exception {
        //生成公钥和私钥
        RSAEncryptUtils encrypt = RSAEncryptUtils.getInstance();
        //加密字符串
        Double message = 1001081.88d;
        System.out.println(message);
        String messageEn = encrypt.encrypt(message);
        System.out.println(messageEn);
        //固定88位
        System.out.println(messageEn.length());
        String messageDe = encrypt.decrypt(messageEn);
        System.out.println(messageDe);
    }

}
